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Novel quantitative trait loci for partial resistance to Phytophthora sojae in soybean PI 398841

Sungwoo Lee, M. A. Rouf Mian, Leah K. McHale, Hehe Wang, Asela J. Wijeratne, Clay H. Sneller, Anne E. Dorrance
Theoretical and applied genetics 2013 v.126 no.4 pp. 1121-1132
Glycine max, Phytophthora sojae, chromosome mapping, crossing, cultivars, disease resistance, genes, genetic markers, genetic resistance, inbred lines, loci, phenotypic variation, quantitative trait loci, resistance mechanisms, root rot, single nucleotide polymorphism, soybeans, stem rot, variance, South Korea, United States
Phytophthora root and stem rot caused by Phytophthora sojae Kaufmann and Gerdmann is one of the most severe soybean [Glycine max (L.) Merr] diseases in the US. Partial resistance is as effective in managing this disease as single-gene (Rps) mediated resistance and is more durable. The objective of this study was to identify novel QTL associated with partial resistance to P. sojae in a new genetic source PI 398841, which originated from South Korea. A population of 305 F7:8 recombinant inbred lines (RILs) derived from a cross of OX20-8 × PI 398841 was used to evaluate partial resistance against P. sojae isolate C2S1 using tray test. The genetic linkage map of this population was constructed with 273 single nucleotide polymorphism and simple sequence markers. Composite interval mapping detected three significant QTL on chromosomes 1, 13, and 18, which accounted for 4 to 16 % of the phenotypic variance. This study also reported six more putative QTL with intermediate significance between chromosome- and genome-wide logarithm of odd (LOD) thresholds, each accounting for only 2 to 3% of the variance. Six of the nine loci were novel. All QTL were located adjacent to known defense-related or disease resistance QTL. Since three QTL on chromosomes 3, 13 and 18 colocalized with known Rps genes PI 398841 was expected to have some Rps genes. However, it was susceptible to 48 isolates of P. sojae tested in this study. PI 398841 is a potential genetic source in improving soybean cultivars for partial resistance to P. sojae.